From what I can tell and what thus far all people with whom I discussed this subject confirmed is that time appears to "accelerate" as we age.

Digging a little, most explanations I found basically reduced this to two reasons:

As we age physically, a time frame of constant length becomes ever smaller in contrast to the time we spent living

As we age socially, we are burdened with an increasing amount of responsibility and thus an increasing influx of information which impairs our perception of the present

To be honest, neither sounds entirely convincing to me because:

In my perception "local time" (short time frames that I don't even bother to measure on the scale of my lifetime) is also accelerating. Just as an example: When I wait for the bus, time goes by reasonably fast as opposed to my childhood tortures of having to wait an eternity for those five minutes to pass.

Even after making a great effort to cut myself off from society and consciously trying to focus on the moment, the perceived speed of time didn't really change. (Although I did have a great time :))

Which leads me to a simple question (and a few corollaries):

Am I just in denial of two perfectly plausible and sufficient explanations, or are there actual biological effects (e.g. changes in brain chemistry) in place, that cause (or at least significantly influence) this?

Is there a mechanism, that "stretches out" time for the young brain so that weight of an immense boredom forces it to benefit from its learning ability, while it "shrinks" time as the brain "matures" and must now act based on what it has learned, which often involves a lot of patience?

If there is such a mechanism, are there any available means to counter it? (not sure I'd really want to, but I'd like to know whether I could)

If I remember correctly it is known that young kids (<4-5 years) cannot distinguish between long and short time frames... I'll look if I can find the proper references about that. I don't know about adult though.\
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nicoJan 12 '12 at 15:23

@back2dos: How far off am I if I paraphrase your question as: "What is a biological/mechanistic explanation of how people learn patience?"
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Steve LianoglouJan 13 '12 at 2:02

@SteveLianoglou I think it's related, but definitely not the same. Patience would be more of a meta-phenomenon of how we emotionally deal with the passage of time, but there are issues of perception that are are more fundamental. See this Nova video(1:40) which touches on this area a little bit. It's more about whether the brain actually slows down than differentiating between 1 second or 2 seconds, but its indicative that this is an active area of interest.
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jonscaJan 13 '12 at 2:32

@jonsca: Thank you, this sounds interesting, however the video is not available in my region :(
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back2dosJan 13 '12 at 12:27

@jonsca: However I googled the guy and saw an interesting talk about possibilianism :)
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back2dosJan 13 '12 at 12:53

5 Answers
5

One important fact to consider is that the perception of time is essentially a recollection of past experience, rather than perception of the present.

Researchers who study autobiographical memory have suggested that part of this effect may be explained by the number of recallable memories during a particular time period. During one's adolescence, one typically has a large number of salient memories, due to the distinctness of events. People often make new friends, move frequently, attend different schools, and have several jobs. As each of these memories is unique, recollection of these (many) memories gives the impression that the time span was large.

In contrast, older adults have fewer unique experiences. They tend to work a single job, and live in a single place, and have set routines which they may follow for years. For this reason, memories are less distinct, and are often blurred together or consolidated. Upon recollection, it seems like time went by quickly because we can't remember what actually happened.

In other words, it can be considered a special case of the availability heuristic: people judge a time span to be longer in which their are more salient events.

Incidentally (and to at least mention biology), episodic memory has been shown to be neurally distinct from semantic memory in the brain. In particular, a double dissociation has been shown for amnesics who suffer from semantic or episodic memory, but not both.

My apologies for the lack of citations, but a good bit about autobiographical memories can be found in:

In particular, emotions such as fear and anxiety tended to "speed up" the passage of time whereas positivity and excitement (particularly with regards to future events) lead to a subjective slowing down of time.

Si it may be just that, as kids, we are just more "excited" in general which made for all those seemingly infinite long summers.

Another possibility is that perhaps it is related to the aging process? As we live longer, I can imagine a scenario where our perception of time would alter (slow down?). It would be interesting to study the perception of the passage of time between long-lived and shorter lived populations in this context.

When we are younger, much like during an emergency, the brain hasn't activated very many filters for sensory data. The young have much to learn about the world and more detail is needed for the brain to make appropriate decisions. Sensory information is recorded in great detail, making time seem to relatively crawl.

As we age, the brain learns to filter out more and more of what it considers inconsequential data.

A good example of these filters at work is the morning commute. If the same route is driven at roughly the same time every workday, the brain begins to leave out much of the repetitive events and scenery from it's historical record of time. Given enough repetition, the record of the event will include so little detail in memory as to almost seem not to have occurred at all. A 30 minute commute will be perceived to have taken very little time -- if it's remembered at all.

As Ferris Bueller so aptly put it, "Life moves pretty fast... You don't stop and look around once in a while, you could miss it."

An intriguing thought, because this correlation exists also for adults, although typically when your heart rate rises, there's a lot of things happening in a short time span, so therefore you have a higher awareness of the individual moment.
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back2dosMar 3 '12 at 11:13

OTOH this would mean that endurance athletes would perceive their lives as very short :D
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back2dosMar 3 '12 at 11:16

1

Not necessarily. Although endurance athletes would have raised heartbeats during exercise, they would have, in general, lower than the mean resting heartrates.
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PoshpawsMar 12 '12 at 11:07

As a child, it could be that the brain is not encoded with a lot of experience. Thus, processing of new information is less complex, and conclusions are made much faster. These conclusions are then encoded into the brain, making future experiences more complex.

A child may have concluded everything it is able to conclude within the first few seconds of arriving at that bus stop.

Second:

A brain with a lot of previous experiences, is able to occupy itself with "trivialities", such as watching snow flakes fall from the sky or thinking about what to have for dinner. Visualizing different tastes and smells.

A grown individual might be slower to conclude, taking more factors into account. It may also have more to ponder on.

Third:

The brain is thinking all the time. It is unconsciously cross referencing every sound, smell and other sense with previous experiences and actually quite busy. If there is a limit to the amount of energy that goes into the brain for processing stuff, a larger and larger percentage of those electrons will be busy "retriggering" signals. Almost like a city road map. It will take a short time for a number of cars to travel every possible route in a small city, than in a big city. Possibly, this has to happen in the brain as well, to refresh old memories.